Process for connecting butane and hexane into isopentane by isomerization and averaging

ABSTRACT

A process for converting butane and hexane into isopentane which comprises (a) isomerizing a C6 rich hydrocarbon stream in an isomerization zone by contacting the C6 rich hydrocarbon stream with an isomerization catalyst at a hydrogen partial pressure between 10 psig and 3,000 psig and a temperature between 100* and 900* F. to obtain a C6 rich effluent stream of increased isohexane content, and (b) averaging at least a portion of the C6 rich effluent stream with butane in an averaging zone by contacting the C6 and butane hydrocarbons with an averaging catalyst having a component which has catalytic activity for alkane dehydrogenation and a component which has catalytic activity for olefin averaging to obtain an iC5 rich stream. Preferably the isomerization step is utilized to simultaneously purify a sulfur contaminated feedstock and isomerize the feedstock before it is fed to the averaging step.

United States Patent Sieg PROCESS FOR CONNECTING BUTANE AND HEXANE INTO ISOPENTANE BY ISOMERIZATION AND AVERAGING [75] Inventor: Robert P. Sieg, Piedmont, Calif.

[73] Assignee: Chevron Research Company, San

Francisco, Calif.

[22] Filed: Oct. 15, 1970 Appl. No.: 80,962

Sieg 260/676 R 1-Set. 25, 1973 Primary Examiner-Delbert E. Gantz Assistant Examiner.luanita M. Nelson Attorney-G. F. Magdeburger, T. G. De Jonghe, J. A. Buchanan, Jr. and R. H. Davies [5 7 ABSTRACT A process for converting butane and hexane into isopentane which comprises (a) isomerizing a C rich hydrocarbon stream in an isomerization zone by contacting the C rich hydrocarbon stream with an isomerization catalyst at a hydrogen partial pressure between 10 psig and 3,000 psig and a temperature between 100 and 900 F. to obtain a C rich effluent stream of increased isohexane content, and (b) averaging at least a portion of the C rich effluent stream with butane in an averaging zone by contacting the C and butane hydrocarbons with an averaging catalyst having a component which has catalytic activity for alkane dehydrogenation and a component which has catalytic activity for olefin averaging to obtain an iC rich stream. Preferably the isomerization step is utilized to simultaneously purify a sulfur contaminated feedstock and isomerize the feedstock before it is fed to the averaging step.

13 Claims, 1 Drawing Figure 7 C4 C 1C5 AVERAGING FRACTIONATION ISOMERIZATION I 2 C5 OR ZONE ZONE ZONE 3 ice 8 hC4-HC5 0R 9 s a V c THRU Ca+ nCs IL BRANCHED CHAIN HYDROCARBONS i A 75 g 20 w v PROCESS FOR CONNECTING BUTANE AND HEXANE INTO ISOPENTANE BY ISOMERIZATION AND AVERAGING BACKGROUND OF THE INVENTION The present invention relates toa combination processinvolving isomerization of saturated hydrocarbons. More particularly, the present invention relates to isomerization operated in combination with saturated hydrocarbon averaging, and preferably with integrated common fractionation facilities.

lsomerizatiorl is a well-known and frequently used step in petroleum refining. Itenables the adjustment of the octane number upwards by converting normal paraffins, such as normal hexane, to isoparaffins, such as 2,2-dimethylbutane. A blend of various isomeric paraffins provides a gasoline which has a higher octane number than a gasoline consisting of normal paraffins. lsomerization is generally performed by passing isomerizable hydrocarbons together with hydrogen through a reaction zone containing an isomerization catalyst. The hydrogen to hydrocarbon mol ratio varies within a wide range, generally from 0.05:1 to :1, preferably within the range of about 0.511 to 2:1 for pentanes and hexanes and 0.1:1 to 1:1 for butanes. The reaction temperature will depend upon the specific hydrocarbons being isomerized and the nature and type of catalyst employed. Hydrocarbon streams consisting chiefly of pentanes and hexanes are usually isomerized at temperatures within the range of 200-900 F. The isomerization, normally effected under pressure, may be carried out in the liquid or vapor phase. Generally, pressures within the rangeof 300 l,000 psig have been used. A liquid hourl'y space velocity (LHSV), that is, the volume of liquid charged per hour per volume of catalyst, within the range of 0.5 to 10.0 and preferably within the range of about 0.75 to 4.0 is employed. Various catalysts have been suggested for use in isomerization processes. In general, the isomerization can be effected at low temperatures (ca. 300 F.) with a Friedel- Crafts catalyst, such as aluminum chloride, or at high temperatures (ca. 750 F.) with a supported metal catalyst, such as platinum onhalogenated alumina or silicaalumina. Thermodynamic equilibrium for isoparaffins is more favorable at low temperatures; however, the low temperature process has not received wide application because the Friedel-Crafts catalyst is quite corrosive and therefore expensive metals or alloys must be used. Of the high temperature isomerization processes, the noble metal catalysts such as platinum or palladium are perhaps considered to be the most effective.

As indicated in U.S. Pat. Nos. 2,951,888 and 3,472,912, minor amounts of sulfur compounds in the.

feed to isomerization processes are harmful for the typical isomerization processes. Catalysts used in typical isomerization processes include composites of a hydrogenating component on an amorphous acidic silicaalumina support and more usually composites comprising halogenated alumina or aluminum, either of which latter composites are herein referred to as halogenated aluminum catalysts.

According to U.S. Pat. No. 2,951,888, a C -C paraffinic feedstock is desulfurized to a sulfur content less than 1 ppm so that better results are achieved in hydroisomerization of the paraffinic feedstock with a catalyst selected from the group consisting of nickel, nickel-molybdenum, and palladium, supported on an acidic silicaalumina support containing 50-90 percent silica, at a temperature of 650 800 F., a pressure of 1,000 psig, and hydrogen/hydrocarbon mol ratio of 0.5 5.0.

U.S. Pat. No. 3,472,912 also discloses an overall combination process involving hydrotreating and isomerization wherein a nickel molybdenum on alumina catalyst is used under hydrotreating conditions to remove sulfur from C C saturated hydrocarbons so that the hydrocarbons can be isomerized with increased life for the isomerization catalyst. Preferred isomerization catalysts according to the process of U.S. Pat. No. 3,472,912 are platinum alumina composites activated by the addition of carbon tetrachloride (thereby resulting in a catalyst which is herein classified as a catalyst containing halogenated aluminum).

More recently, catalysts comprising either natural or synthetic crystalline aluminosilicates have been suggested for isomerization processes. Included among the crystalline aluminosilicates which have been suggested are the type X and type Y silicates, mordenite, and layered aluminosilicates such as described in Granquist U.S. Pat. No. 3,252,757.

U.S. Pat. No. 3,507,931, titled lsomerization of Paraffinic Hydrocarbons in the Presence of a Mordenite Catalyst discloses the isomerization of straight-run distillates rich in C C normal paraffins using a catalyst having a high silica to alumina ratio, preferably above 20:1 and operating the isomerization reaction at relatively low temperatures, such as 250 400 F.

U.S. Pat. Nos. 3,280,212 and 3,301,917 also disclose hydroisomerization processes using crystalline aluminosilicate type catalysts.

As indicated above, the present invention is directed to a combination process involving isomerization and averaging. The term averaging is used in this specification to mean conversion of feed components or hydrocarbon molecules of different molecular weight to components of intermediate molecular weight relative to the feed components. For example, in an averaging reaction between butane and hexane, the butane and hexane are converted to pentane.

Averaging of saturated hydrocarbons or paraffinic hydrocarbons to form hydrocarbons of intermediate molecular weight has been carried out according to prior art, using acidic catalysts, such as boron fluoridehydrogen fluoride catalyst. For example, U.S. Pat. No. 2,216,274 discloses a process for interacting relatively high molecular weight paraffin hydrocarbons with lower molecular weight isoparaffin hydrocarbons to form paraffin hydrocarbons of intermediate molecular weight by contacting the feed hydrocarbons with a catalytic material consisting essentially of boron fluoride and hydrogen fluoride at temperatures between about -30 and C.

A number of other patents disclose paraffin averaging reactions using a catalyst comprised essentially of boron fluoride and hydrogen fluoride or boron fluoride, hydrogen fluoride and water. These patents include U.S. Pat. Nos. 2,296,371, 2,405,993, 2,405,994, 2,405,995, 2,405,996 and 2,405,997.

Particularly advantageous averaging reaction conditions for use in the averaging step of the present invention are disclosed in patent applications Ser. Nos. 864,870 and 864,871, which applications have the same assignee as the present application.

SUMMARY OF THE INVENTION According to the present invention, a process is provided for converting butane and hexane into isopentane which comprises (a) isomerizing a C rich hydrocarbon stream in an isomerization zone by contacting the C, rich hydrocarbon stream with an isomerization catalyst at a hydrogen partial pressure between 10 psig and 3,000 psig and a temperature between 100 and 900 F. to obtain a C rich effluent stream of increased isohexane content, and (b) averaging at least a portion of the C rich effluent stream with butane in an averaging zone by contacting the C and butane hydrocarbons with an averaging catalyst having a component which has catalytic activity for alkane dehydrogenation and a component which has catalytic activity for olefin averaging to obtain a stream containing isopentane (iC The iC containing stream from the averaging zone usually contains at least volume percent iC The process of the present invention results in the production of high octane isopentane from low octane hexane (such as normal hexane, which has an octane rating of about 26) and butanes which often are currently present in excess amounts in refinery plants. Butanes have become increasingly available as refinery plants have been modernized to include hydrocracking units producing substantial amounts of butanes and as lower vapor pressures have been required for gasolines, necessitating the use of less of the relatively volatile butanes in gasolines. The isopentane which is produced in the process of the present invention has an octane rating of about 92 and is particularly useful in high octane unleaded or low lead content gasolines. lsomerization of C hydrocarbons can be used to upgrade the octane rating of normal hexane-rich hydrocarbon fractions. However, the octane can be increased only to about 70 75 (motor octane) by isomerization because the main hexane isomers produced, namely, Z-methyl pentane and 3-methyl pentane, have an octane rating of only 73 and 75, respectively. Although increasing the octane rating of a C fraction from the vicinity of about 26, which is the octane of normal hexane, to about 70 75 by isomerization to produce isohexanes represents a substantial increase, it is generally not a sufficient increase to produce high octane gasoline components for use in unleaded or lead-free gasolines.

The C rich hydrocarbons also have been considered as feedstocks for catalytic reforming in order to reform the C, material into reasonably low volatility gasoline boiling range range hydrocarbons in the 90+ octane range. However, the C hydrocarbons have been found to make a relatively unattractive feedstock for catalytic reforming processes.

Butanes have a high octane rating, with normal butane having an octane rating of about 90 and isobutane having an octane rating of about 99. However, as indicated previously, only limited amounts of butanes can be used in motor gasolines before exceeding Ried Vapor Pressure limitations for the gasoline.

Thus, it is desirable to provide a process for upgrading C, rich hydrocarbon fractions into 90+ octane rating components and it is also desirable to upgrade C hydrocarbons into high octane gasoline boiling range hydrocarbons which are not as volatile as the C hydrocarbons. The process of the present invention achieves these desired results by the combination of isomerization with averaging. in addition, in accordance with the preferred embodiment of the present invention wherein a sulfur containing feedstock is fed to the isomerization zone, the isomerization step is particularly advantageously employed with the averaging step as the isomerization step serves the dual function of l) purifying C rich hydrocarbons which are subsequently reacted with butanes in the averaging zone and (2) isomerizing the C hydrocarbons so that the amount of isopentane produced in the averaging zone will be increased.

The isomerization zone serves to purify the feed for the averaging zone by converting sulfur compounds in the C rich feed to the isomerization zone to hydrogen sulfide which can be readily removed from the isohexane-rich effluent from the isomerization zone before the isohexane-rich effluent is fed to the averaging zone. The preferred catalyst used in the averaging zone is sensitive to even small amounts of H 8 and H 8 will be formed in the averaging zone unless the organic sulfur compounds are substantially completely removed ahead of the averaging zone.

The isomerization zone serves to increase the amount of isopentane produced in the averaging zone by providing a branched chain C feed for the averaging zone. Using the preferred dual function dehydrogenationolefin averaging catalyst for the averaging zone, there is substantially no production (or depletion) of branched chain hydrocarbons in the averaging reaction zone. Thus, if normal hexane is fed to the averaging zone, the reaction of the normal hexane with normal butane will produce primarily normal pentane. However, if isohexane is fed to the averaging zone and reacted with normal butane, then a substantial amount of isopentane will result from the averaging of the isohexane with the normal butane.

in the process of the present invention, it is particularly preferred to further integrate the isomerization zone and the averaging zone using common fractionation facilities to a substantial extent. Preferably, the effluent from the averaging zone is fractionated to distill out not only product isopentane produced as a result of the combined operation of the isomerization and averaging zones, but also to fractionate out a normal pentane rich stream for recycle to the isomerization zone. The normal pentane preferably is isomerized to isopentane in the isomerization zone and then is separated from the effluent from the isomerization zone as an isopentane product before the C rich effluent from the isomerization zone is fed to the averaging zone.

In accordance with another preferred embodiment, the common fractionation zone is used to separate a product purified iC from the effluent from the averaging zone and to obtain a C rich fraction which preferably is recycledto the averaging zone for reaction with butanes. In some instances, a normal hexane-rich portion of the C fraction from the fractionation zone is preferably separated from the isohexane constituents and the normal hexane-rich portion is recycled to the isomerization zone, but it is usually preferably to recycle the C fraction from the fractionation zone primarily to the averaging zone because the C, fraction is rich in isohexane, having previously passed through the isomerization zone.

As indicated above, one of the important purposes which the isomerization zone preferably serves in the process of the present invention is to remove sulfur impurities from the C fraction before the C fraction is bon streams which are essentially free of sulfur impuri ties as, for example, C hydrocarbon streams obtained from a catalytic reforming unit. However, the process combination ofthe present invention has particular advantage when applied to C rich hydrocarbon streams containing minor amounts of sulfur impurities,'usually at least ppm sulfur.

C hydrocarbon cuts obtained by crude oil distillation, i.e., straight-run C rich hydrocarbon fractions,

' e.g., naphtha fractions, contain usually at least 5 ppm sulfur compounds and generally between about 20 and 500 ppm sulfur compounds. The isomerization zone can use a hydrotreating step ahead of the isomerization reaction zone catalyst as in the case of using halogenated aluminum type catalysts, but it is preferred in the process of the present invention to use a crystalline aluminosilicate type catalyst, many of which catalysts we have found can be operable with several hundred ppm sulfur and frequently up to about 500 or 1,000 ppm sulfur in the feed without substantially decreasing the life of the hydroisomerization catalyst. Also, the crystalline aluminosilicate type catalyst can be used to obtain relatively high yields of isohexane per pass at temperatures usually about 100 F. less than is required for. a comparable isohexane yield using halogenated aluminum type isomerization catalysts. I-Ialogenated aluminum type catalysts which are sensitive to sulfur poisons and thus not as preferred for use in the process of the present invention include the catalyst such as used in the butamer process described in the Oil and Gas Journal, Vol. 56, No. 13, Mar. 31, 1958, pp. 73-76, the BP isomerization process as described in Hydrocarbon Processing, Vol. 45, No. 8, Aug. 1966, pp. 168-170, and the liquid phase isomerization process described in Hydrocarbon Processing, Vol. 42, No. 7, July 1963, pp. 125-130.

Thus, in the process of the present invention it is preferred to use a hydroisomerization catalyst which is essentially free of halogenated aluminum. Catalysts comprising crystalline aluminosilicates, such as molecular sieves, mordenite, and layered crystalline aluminosilicate. Palladium and platinum are preferred hydrogenation components. Preferred catalysts comprising crystalline aluminosilicate and a hydrogenation component such as palladium or others are described in patent applications Ser. Nos. 776,773 now abandoned, and 839,999 now U.S. Pat. No. 3,617,490, which applications are incorporated by reference into the present patent application, particularly those portions of the afore-identified applications disclosing catalyst compositions. Preferred aluminosilicate containing catalysts for use in the isomerization zone include catalysts comprising a layered clay-type aluminosilicate cracking component; with 0.01 and 2.0 weight percent, based on said cracking component and calculated as the metal, ofa hydrogenating component selected from platinum, palladium, iridium, ruthenium, and rhodium; and also with 0.01 to 5.0 weight percent, based on said cracking component and calculated as the metal, of a hydrogenating component selected from tungsten and chromium. Particularly preferred hydroisomerization catalysts are those as described above wherein the hydrogenating components are palladium and chromium. In the present specification, oxides and other compounds of metals are to be considered as included in reference to a metal simply as an element, i.e., chromium includes the use of chromium in compound forms such as chromium oxide.

In the process of the present invention, various catalysts can be used in the averaging zone for the averaging reaction between hexanes and butanes to produce pentanes. However, it is greatly preferred to use catalyst compositions as described in applications Ser. Nos.

864,870 now abandoned, and 864,871. Thus, preferred catalysts are catalytic masses comprising a component which has catalytic activity for dehydrogenation, and a component which has catalytic activity for olefin averagingfPreferably, the catalytic mass comprises a platinum group metal or metal compound on a refractory support and a Group VIB metal compound on a refractory support. The disclosures of Ser. Nos. 864,870 now abandoned, and 864,871 are incorporated by reference into the present patent application, particularly those portions of the disclosure pertaining to dehydrogenation-olefin averaging catalyst compositions and preferred operating conditions using those catalysts. Preferred averaging zone reaction conditions for use in the process combination of the present invention which are discussed in more detail in Ser. No. 864,871 comprise contacting butanes and a paraff'mic C rich hydrocarbon fraction with a catalytic mass comprising platinum on alumina andtungsten or tungsten oxide on silica at a temperature between about 650 and 950 F. and a pressure between about psia and 1,500 psia. Preferably, the olefin concentration in the averaging reaction zone is maintained below 5 volume percent.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a schematic process flow diagram il-' lustrating preferred embodiments of the present invention.

DETAILED DESCRIPTION Referring now more particularly to the drawing, a C rich hydrocarbon stream is fed via line 1 to isomerization zone 2. The C fraction or cut can be obtained from the effluent from a catalytic reforming process and advantageously upgraded in the process of the present invention to isopentane. However, the process combination of the present invention has particular application to striaght-run hydrocarbon C rich fractions containing organic sulfur compounds, usually in an amount between about 5 ppm and 300 ppm.

The C rich hydrocarbon fraction is isomerized in the presence of hydrogen using a hydroisomerization catalyst which preferably comprises a cyrstalline aluminosilicate together with a hydrogenation component such as palladium or platinum. Preferred operating conditions for the C isomerization include a hydrogen gas rate in the range of 1,000 to 5,000 SCF/b, preferably 1,500 to 2,000 SCF/b.; space velocities in the range of about 0.1 to 20 liquid volumes per hour per volume of catalyst, preferably 1.0 to 5.0 LHSV; temperatures in the range of about 200 to 800 F., preferably 250 to 750 F.; and pressures within the range of atmospheric to 3,000 psig, preferably in the range of 500 to 800 psig.

1n isomerization zone 2, the normal hexane-rich feed is isomerized to an isohexane-rich effluent. The term rich" is used in the present specification to mean a content of at least 25 percent of the specified component and generally 50 percent or more of the specified component. isohexane is used herein to include the branched chain hexanes and exclude normal hexane.

After stripping hydrogen sulfide from the isohexanerich effluent from the isomerization reaction zone, the isohexane-rich fraction is fed via line 3 and then 4 to averaging zone 5. The main averaging reaction in zone 5 is:

Butane Hexane 2 Pentane Molecules As indicated previously, the reaction preferably is carried out in the presence of a dehydrogenation-olefin averaging catalyst mass at a temperature preferably below 950 F. The amount of iC withdrawn in the effluent from the averaging zone via line 6 is increased over what would be obtained in the case of a normal hexane-rich feed because isomerization zone 2 serves to cause branching of the hexane molecules to thus give an isohexane-rich reed for the averaging zone which in turn results in an increased amount of isopentane in the effluent from the averaging zone.

Butanes are fed to the averaging zone via lines 7 and 8. Fresh feed butanes are brought in via line 7. According to one preferred alternate embodiment of the present invention, the fresh feed butanes are derived from a hydrocracking unit as effluent butanes from hydrocracking contain more than an equilibrium amount of isobutane, usually about 9 parts isobutane to 1 part normal butane. isobutane is formed due to the reaction mechanism in hydrocracking and does not have sufficient time to equilibrate with normal butane before the reaction products are withdrawn from the hydrocracking reaction zone and cooled to a lower temperature. As is the case with isohexane, the isobutane feed increases the amount of isopentane obtained in the averaging zone.

Exemplary conditions for butane-hexane averaging are essentially the same as the following conditions employed in the averaging of normal butane and normal octane.

Volume of Catalyst in Reactor: 9 cubic centimeters Catalyst: 2 cc. of 0.5 wt. percent PL; 0.5 wt. percent Re, and 0.5 wt. percent Li on M 0 and 7 cc. of 8.0 wt. percent W0, on SiO,, for a total of 9 cc. of catalyst.

Both types of catalyst particles were 28 to 60 Tylermesh size, and the catalyst particles were uniformly mixed together.

Operating Conditions:

Temperature: 800F.

Pressure: 900 psig Feed Rate: 3 cc./hour of normal butane 6 cc./hour of normal octane The product as shown below in Table l was obtained after operating for one hour in accordance with the above operating conditions.

TABLE 1 Product (1) Weight percent q 1.10 C,H 6.26 C 11,, 20.60 C,H,, 9.95 C,H,, 9.72 C,H 9.24 C,H,, 21.75 C,H,., 6.87 C H 5.00 C H 3.52 C ll, 2.60 C to C, 2.89

1. Before analysis, the product was hydrogenated over a platinum-silica catalyst so that all product components were measured as alkanes (approximately one weight percent olefins was present in the total product before hydro-genating).

The above results illustrate the averaging of saturated hydrocarbons (alkanes) to obtain intermediate molecular weight hydrocarbons. A yield of 28.91 weight percent intermediate (C C and C,) hydrocarbons was obtained in nonrecycle operation at a temperature of 800 F.

Table ll below compares results for four runs at varying n-octane to n-butane feed ratios. The operating conditions were the same as those set out above, except for the ratio of n-C to n-C TABLE 11 Intermediate Feed Products (Wt. Product (Wt. (vol. Total of C, C, C C C, C,, C, and C, 0 K10 137 4 24 33 67 1310.5 7.5 31 67 33 1010.5 9.5 29 0 7 8 9 24 The results shown above in Table 1] illustrate that the n-C and n-C, feed constituents interact to form intermediate products, i.e., C C and C,s. If the n-C n-C feed was simply disproportionated, a yield of about 24 weight percent C C C, intermediate product would be obtained. When 100 percent n-C is fed (and thus disporportionated) a yield of 24 weight percent n-C C C, is obtained. But when a mixture of n-C and n-C is fed, a yield of about 29 to 31 weight percent C C C, is obtained. The increase of about 25 weight percent C C,, C, when the mixture of n-C and n-C is fed illustrates that the n-C, and n-C are interacting or undergoing averaging reactions, rather than simply or only being disproportionated.

Effluent from the averaging zone containing iC, is passed via line 6 to fractionation zone 9 wherein product isopentane is separated and withdrawn via line 10. Light hydrocarbons, usually propane and lighter, which are generated in the averaging zone or in the isomerization zone are withdrawn from the fractionation zone via line 11. Unreacted butanes are withdrawn via line 12 and preferably are recycled to the averaging zone via lines 13 and 8. In accordance with an alternate preferred embodiment, at least a portion of the butanes are recycled via line 14 to isomerization zone 2 to in crease the isobutane content of the butane stream so that the product from the averaging zone will be higher in isopentane content as opposed to normal pentane.

A normal pentane-rich stream can be fractionated from isopentane in the fractionation zone and recycled via line 15 to isomerization zone 2. As schematically indicated in the drawing, isopentanes can be stripped from the effluent from the isomerization reactor and removed as a product via line 16 rather than feeding the isopentane to the averaging zone along with the hexanes from the isomerization zone.

Unreacted hexanes are preferably separated as a hexane-rich fraction in zone 9 and recycled via lines 17 and 18 to averaging zone 5.

According to a preferred alternate embodiment, the entire effluent, or at least the normally liquid effluent from zone 2 is fed to common fractionation zone 9 to separate out feed material for averaging zone 5.

in some instances, it is preferable to withdraw a separate stream of heavier hydrocarbons from zone 8 via 9 lines 119 and 20 for use asa gasoline component. Thus, C, hydrocarbons can be withdrawn from fractionation zone 9 via lines 19 and 20. However, in most instances, it is more advantageous to simplify fractionation zone 9 so that there is substantially only one bottoms stream withdrawn from the fractionation zone, which bottoms stream is a C rich stream containing some C,+ hydrocarbons. This C stream containing C and C hydrocarbons is advantageously recycled via line 118 to the averaging zone for the production of isopentane and normal pentane.

The fractionation zone can contain a number of different distillation or separation facilities. However, preferably, the three basic units in the fractionation zone are a depropanizer distillation column from which a C fraction is withdrawn, a diesobutanizer from which isobutanes are preferably withdrawn for recycle to the averaging zone 5, and a diesopentanizer from which product isopentane is withdrawn as an overhead stream, normal pentane is withdrawn as a sidestream for recycle to the isomerization zone and a CM stream is withdrawn for recycle to theaverageing zone. Typically, these basic distillation columns operate sequentially with the bottoms from the depropanizer being the feed to the deisobutanizer and the bottoms from the deisobutanizer being the feed to the deisopentanizer. Preferably, a normal butane stream is withdrawn as a sidestream from the deisobutanizer and the normal butane is recycled to isomerization zone 2 for isomerization to isobutane to aid in increasing the isopentane content of the averaging zone effluent.

Although various embodiments of the invention have been described, it is to be understood that they are meant to be illustrative only and not limiting. Certain features may be be changed without departing from the spirit or scope of the present invention. It is apparent that the present invention has broad application to the combination of isomerization of C hydrocarbons in combination with the averaging of C and C5 hydrocarbons. Accordingly, the invention is not to be construed as limited to the specific embodiments or examples discussed but only as defined in the appended claims or substantial equivalents of the claims.

I claim:

11. A process for converting butane and hexane into isopentane which comprises:

a. isomerizing normal hexane in an isomerization zone by contacting the hexane with an isomerization catalyst at a hydrogen partial pressure between psig and 3,000 psig and a temperature between 100 and 900 F. to obtain an effluent stream containing normal hexane and at least 25 weight pen cent isohexane, and

b. reacting at least a portion of the effluent stream hexanes with butane in an averaging zone to obtain components of intermediate molecular weight relative to hexane and butane. wherein the reacting is carried out by contacting the hexane and butane hydrocarbons with a catalyst mass comprising a platinum group metal or metal compound on a refractory support and a Group VlB metal compound on a refractory support, and at a temperature between 650 and 950 F. and a pressure between 100 psia and 1,500 psia, to obtain a stream containing isopentane.

2. A process in accordance with claim 11 wherein at least a portion of the stream containing isopentane is fractionated in a fractionation zone to obtain a purified isopentane stream and a normal pentane-rich'stream and wherein the normal pentane-rich stream is'recycled to the isomerization zone.

3. A process in accordance with claim 1 wherein at least a portion of the stream containing isopentane is fractionated in a fractionation zone to obtain a purified isopentane stream and a hexane-rich fraction and wherein the hexane-rich fraction is recycled to the averaging zone.

41. A process for converting butane and hexane into isopentane which comprises:

a. isomerizing a normal hexane stream containing at least 5 ppm sulfur compounds in an isomerization zone by contacting the normal hexane with an isomerization catalyst at a hydrogen partial pressure between 10 psig and 3,000 psig and a temperature between and 900 F. to obtain an effluent stream of reduced sulfur content and containing normal hexane and at least 25 weight percent isohexane, and

b. reacting at least a portion of the effluent stream hexanes with butane in an averaging zone to obtain components of intermediate molecular weight relative to hexane and butane, wherein the reacting is carried out by contacting the hexane and butane hydrocarbons with a catalyst mass comprising a platinum group metal or metal compound on a refractory support and a Group VIB metal compound on a refractory support, and at a temperature between 650 and 950 F. and a pressure between 100 and 1,500 psia, to obtain a stream containing isopentane.

5. A process in accordance with claim 4 wherein the hexane rich hydrocarbon stream fed to the isomerization zone is a straight-run fraction obtained by fractionating a hexane rich cut from crude oil.

6. A process in accordance with claim t wherein the catalyst used in the isomerization zone is substantially free of halogenated aluminum.

7. A process in accordance with claim 41 wherein the isomerization catalyst comprises palladium or platinum and a crystalline aluminosilicate material.

b. A process in accordance with claim 41 wherein the isomerization catalyst comprises 0.05 to 5.0 weight percent palladium and 0.05 to 5.0 weight percent chromium on a layered clay type crystalline aluminosilicate component.

9. A process in accordance with claim 11 wherein the averaging reaction comprises contacting the hexane and C, hydrocarbon feed with a catalytic mass comprising platinum on alumina and tungsten or tungsten oxide on silica at a temperature between about 650 and 900 F. and a pressure between about 100 psia and 1,500 psia.

110. A process in accordance with claim 9 wherein the olefin concentration in the averaging reaction zone is maintained below about 5 volume percent.

1.1. A process for converting butane and hexane into isopentane which comprises:

a. isomerizing a normal hexane stream containing between 5 and 500 ppm organic sulfur compounds in an isomerization zone by contacting the normal hexane with a sulfactive isomerization catalyst at a hydrogen partial pressure between about 100 and 1,500 psig and a temperature between about 200 and 800 F. to obtain an effluent stream containing less than 1 ppm sulfur and between 5 and 100 percent isohexane, and

b. reacting at least a portion of the effluent stream hexanes with normal butane in an averaging zone to obtain components of intermediate molecular weight relative to hexane and butane, wherein the reacting is carried out by contacting the hexane and normal butane with an averaging catalyst comprising a platinum group metal on a refractory support and a Group VlB metal on a refractory support at a temperature between 400 and 900 F. to obtain a stream containing isopentane.

12. A process in accordance with claim 11 wherein at least a portion of the stream containing isopentane is fractionated in a fractionation zone to obtain a purified isopentane stream and a normal pentane-rich stream and wherein the normal pentane-rich stream is recycled to the isomerization zone.

13. A process in accordance with claim 11 wherein at least a portion of the stream containing isopentane is fractionated in a fractionation zone to obtain a purified isopentane stream and a hexane-rich fraction and wherein the hexane-rich fraction is recycled to the averaging zone.

zgz gg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,761,535 I Dated September 25, 1973 Inventor(s) Robert P. Sieg It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title Page and Col. 1, change title from "PROCESS FOR CONNECTING BUTANE AND HEXANE INTO ISOPEN'IANE BY ISOMERIZA- TION AND AVERAGING" to PROCESS FOR CONVERTING BUTANE AND HEXANE IN'lO ISOPENTANE BY ISOMERIZA- IION AND AVERAGING-.

Col. 6, line 46, -"striaght-run" should read --straight-run--.

Col. 6, line 52 "cyrstalline" should read -cryst'al1ine-.

Col. ;7, line 18, "reed" should read -feed-.

Col.'8, line 4, "hydro-genating" should read --hydrogenating--.

Col. 8, lines 19-23, "C C should read --C C Col, 9, line 59, "butane. wherein" should read --butane, wherein-.

Signed and sealed this 9th day of April 197b,.

(SEAL) Atteat:

EDWARD M.FLETGHER,JR. C. MARSl-IALL DAMN attesting Officer Commissioner of Patents 

2. A process in accordance with claim 1 wherein at least a portion of the stream containing isopentane is fractionated in a fractionation zone to obtain a purified isopentane stream and a normal pentane-rich stream and wherein the normal pentane-rich stream is recycled to the isomerization zone.
 3. A process in accordance with claim 1 wherein at least a portion of the stream containing isopentane is fractionated in a fractionation zone to obtain a purified isopentane stream and a hexane-rich fraction and wherein the hexane-rich fraction is recycled to the averaging zone.
 4. A process for converting butane and hexane into isopentane which comprises: a. isomerizing a normal hexane stream containing at least 5 ppm sulfur compounds in an isomerization zone by contacting the normal hexane with an isomerization catalyst at a hydrogen partial pressure between 10 psig and 3,000 psig and a temperature between 100* and 900* F. to obtain an effluent stream of reduced sulfur content and containing normal hexane and at least 25 weight percent isohexane, and b. reacting at least a portion of the effluent stream hexanes with butane in an averaging zone to obtain components of intermediate molecular weight relative to hexane and butane, wherein the reacting is carried out by contacting the hexane and butane hydrocarbons with a catalyst mass comprising a platinum group metal or metal compound on a refractory support and a Group VIB metal compound on a refractory support, and at a temperature between 650* and 950* F. and a pressure between 100 and 1,500 psia, to obtain a stream containing isopentane.
 5. A process in accordance with claim 4 wherein the hexane rich hydrocarbon stream fed to the isomerization zone is a straight-run fraction obtained by fractionating a hexane rich cut from crude oil.
 6. A process in accordance with claim 4 wherein the catalyst used in the isomerization zoNe is substantially free of halogenated aluminum.
 7. A process in accordance with claim 4 wherein the isomerization catalyst comprises palladium or platinum and a crystalline aluminosilicate material.
 8. A process in accordance with claim 4 wherein the isomerization catalyst comprises 0.05 to 5.0 weight percent palladium and 0.05 to 5.0 weight percent chromium on a layered clay type crystalline aluminosilicate component.
 9. A process in accordance with claim 1 wherein the averaging reaction comprises contacting the hexane and C4 hydrocarbon feed with a catalytic mass comprising platinum on alumina and tungsten or tungsten oxide on silica at a temperature between about 650* and 900* F. and a pressure between about 100 psia and 1,500 psia.
 10. A process in accordance with claim 9 wherein the olefin concentration in the averaging reaction zone is maintained below about 5 volume percent.
 11. A process for converting butane and hexane into isopentane which comprises: a. isomerizing a normal hexane stream containing between 5 and 500 ppm organic sulfur compounds in an isomerization zone by contacting the normal hexane with a sulfactive isomerization catalyst at a hydrogen partial pressure between about 100 and 1,500 psig and a temperature between about 200* and 800* F. to obtain an effluent stream containing less than 1 ppm sulfur and between 5 and 100 percent isohexane, and b. reacting at least a portion of the effluent stream hexanes with normal butane in an averaging zone to obtain components of intermediate molecular weight relative to hexane and butane, wherein the reacting is carried out by contacting the hexane and normal butane with an averaging catalyst comprising a platinum group metal on a refractory support and a Group VIB metal on a refractory support at a temperature between 400* and 900* F. to obtain a stream containing isopentane.
 12. A process in accordance with claim 11 wherein at least a portion of the stream containing isopentane is fractionated in a fractionation zone to obtain a purified isopentane stream and a normal pentane-rich stream and wherein the normal pentane-rich stream is recycled to the isomerization zone.
 13. A process in accordance with claim 11 wherein at least a portion of the stream containing isopentane is fractionated in a fractionation zone to obtain a purified isopentane stream and a hexane-rich fraction and wherein the hexane-rich fraction is recycled to the averaging zone. 